The penhexo is equal to s(5,5,6) in strong array notation. [1] The term was coined by wiki user Hyp cos. It can be represented in up-arrow notation as \(5\uparrow\uparrow\uparrow\uparrow\uparrow\uparrow5\) (5 octated to 5).

This number is also equal to s(5,2,7) and s(5,6,1,2).


The name of this number is based on the word "penta" and "hexa" (Greek for 5 and 6), meaning a base-5 number, generated using hyper-6 operation based on exponentiation.


Notation Approximation
Up-arrow notation \(5\uparrow\uparrow\uparrow\uparrow\uparrow\uparrow5\) (exact)
BEAF \(\{5,5,6\}\) (exact)
Hyper-E notation \(E(5)1\#1\#1\#1\#1\#5\) (exact)
Chained arrow notation \(5\rightarrow5\rightarrow6\) (exact)
Hyperfactorial array notation \(6!5\)
Fast-growing hierarchy \(f_7(4)\)
Hardy hierarchy \(H_{\omega^7}(4)\)
Slow-growing hierarchy \(g_{\varphi(5,0)}(5)\)


  1. Numbers from linear array notation | Steps Toward Infinity!

See alsoEdit

Hyp cos' linear strong array notation numbers | exAN numbers
3-entry series
Tribo group: tribo · tetbo · pentbo · hexabo
Trientri group: trientri · tettro · pentro · hextro
Trientet group: triteto · trientet · penteto · hexteto
Trienpent group: tripeno · tetpeno · trienpent · hexpeno
Trienhex group: trihexo · tethexo · penhexo · trienhex

Ad blocker interference detected!

Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.